1½ ounces unsweetened cocoa powder (approx ½ C)
3 C half-and-half
1 C heavy cream
8 egg yolks
9 ounces sugar
2 tsp vanilla
Place cocoa powder and 1 cup half-and-half in saucepan over medium heat; whisk to combine. Add remaining half-and-half and heavy cream. Bring to a simmer, stirring occasionally; remove from heat.
Whisk egg yolks until they lighten in color. Gradually add sugar; whisk to combine. Temper cream mixture into eggs and sugar by gradually adding about 1/3 of the cream mixture. Return entire mixture to saucepan; place over low heat.
Continue to cook, stirring frequently, until mixture thickens slightly and reaches 175° F. Allow mixture to sit at room temperature 30 minutes. Stir in vanilla extract. Place the mixture into the refrigerator; when cool enough not to form condensation on the lid, cover and store for 4 to 8 hours or until the temperature reaches 40° F or below.
Process in ice cream maker according to manufacturer's directions (approx 25-35 minutes). Serve immediately, or freeze in airtight container for firmer consistency.
I stirred in some chunks of homemade toffee during the last minute or two in the ice cream maker. Other add-ins -- nuts, fruit, marshmallows, candy chunks, cookie crumbs -- could also be delicious!